Hey there, I did some research on this because I already got asked about android saves in specific.
On PC, it's fairly easy, you just need to make sure you keep your save files which are stored in:
%appdata%/RenPy/BetweenHumanity-1679746291
On android, I've done everything on the RenPy side that is necessary to store the saves and automatically detect them again.
The saves are stored in:
/Android/data/com.dbpanda.betweenhumanity/files/game/saves
If you delete the game and all it's data on an android phone, it will of course delete the saves as well. I'm not sure if you can delete the game and retain the data. But as far as your question goes, if you store the save files separately, you'll never loose them. Just make sure to back them up if you switch phones or PCs. :)